Feeding means for arc lamps



T. HALL FEEDING MEANS FOR ARC LAMPS May 3 1927.

Filed Oct. 13, 1923 2 Sheets-Sheet 1 lllrll/llllllllll [III/IIIII/l/lgyweutoz MW May 3 1927. 1,626,932

T. HALL FEEDING MEANS FOR ARC LAMPS Filed Oct. 15, 1925 2 Sheets-sheet 2MI I ,n umm.

V -wmnmmm" 4 HHQIIIIIIIHIH 4 I m 40 avwemtoz Patented May 3, 1927.

UNITED STATES PATENT OFFICE.

THEODORE HALL, OF BROOKLYN, NEW YORK, ASSIGNOR 'lO HALL & CONNOLLY,INCL, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

FEEDING MEANS FOR ARC LAMPS.

Application filed. October 13, 1923. Serial No. 668,273.

This invention relates to feeding mechanisms for are lamps especiallyprojector lamps for motion or other pictures. In such lamps it isdesirable to provide an automatic feed for both electrodes, both tomaintain the proper arc length and the proper position of the positivecrater with respect to the projector. According to my invention 1provide a single means for both purposes which feeds the electrodestogether at a predetermined rate in accordance with the arc length. Myinvention has particular reference to the contact means which governsthe automatic power driven feeding means, whereby a quick break, selfcleaning contact is provided.

A further object of the invention is to so design the automatic meansthat it does not interfere with the hand feed.

Further objects of the invention will be apparent as the descriptionproceeds.

Referring to the drawings wherein I have shown the preferred forms of myinvention,

Fig. 1 is a skeleton side elevation of the mechanism of a projector lampin accord:

ance with my invention.

Fig. 2 is an end view of the same, the parts being in section.

Fig. 3 is an elementary wiring diagram.

Fig. at is a view corresponding to Fig. 1, of a modified form of theinvention.

Fig. 5 is a detail of one of the contacts of Fig. 4-.

The skeleton of a projector is shown in Figs 1, 1 representing thereflector, 2, the negative carbon, 3, the positive carbon, and

16 the back plate. 'Each holder 4 and 5 is threaded on a feed screw 6,the threads having an opposite pitch at the two ends as at 7 and 8 sothat rotation of the screw will feed both electrodes together (orapart). Also the pitch of the two threads is designed so thateachelectrode is fed at its proportionate rate of consumption tomaintain the positive crater at the focus of, the projector. Thepositive electrode is shown as yieldingly clamped in its holder byspring pressed plunger 9.

For efiecting the automatlcfeed, I provide a motor 10, which in thisinstance turns feed rod 6 by means of a pawl and ratchet mechanism. Themotor is shown as provided with a worm l1 meshing with worm wheel. 12.On the shaft 13 of said wheel is crank pin 14 to which is connectedconnecting rod 15. Said rod in turn is pinned to pawl carriage 17,carrying pawl 18. The cooperating iatchet wheel 19 may be directlymounted. on feed rod 6 on which may also be located the hand feedingknob 20.

I prefer to reciprocate the carriage only when feeding is desired andtherefore provide means for governing the motive means as feeding isnecessary. For this purpose a control or voltage regulator coil 22,connected preferably across the arc, is provided. Said coil is shown asin the form of an electro-magnet having a core 23 and armature 24pivoted at 25. Said armature is provided with a downwardly extending arm26 having a contact 27 at its lower end. An adjustable spring 28normally holds the arm 26 to the left in Fig. 1 against stop'29, thusholding armature '24 up. As the arc length increases, the strength ofthe coil increases until the tension of spring 28 is overcome andcontact 27 brought against cooperating contact 30, which is located onreciprocating carriage 17. Thus, whenever the contacts are closed, arelative movement is imparted to the contacts to keep their surfacesclean and bright.

Preferably, 1 construct contact 30 with an inclined surface 31 whichslopes outwardly toward contact 27 in the direction of pawl 18. By thismeans I provide for a quick, definite break of the contact and insureits always occurring when the pawl is up, i. e., out of engagement withthe ratchet, thus leaving the screw 6 free to be fed by hand. That thisis so will be appreciated when it is remembered that the pull of magnet22 on armature 24 varies inversely as the square of the air gap, anddirectly in accordance with the current strength due to the voltage dropacross the are. Thus when the arc is too long and coil 22 is strongenough, contacts 27 and 30 are closed and remain closed under the pullof the magnet on the armature is overbalanced by spring 28. The air gapis of course longest at the high point of contact 30 and therefore, thepull is weakest at that point. Hence the magnetic pull will first beovercome at this point. To assist this action the tension of spring 28is so designed that its rate of increase for a given elongation is notnearly as great as the increase in magnetic pullon the armature for acorresponding shortening of the air gap. This construction, it should benoted alsohas the decided advantage that the two contacts are heldtogether much more tightly during the greater portion of their movementthan is ordinarily the ,case, since the pull of magnet 22 on contact 27is greater at all positions of contact 30 than at the high spot, wherethe contact is made.

One modification that my invention may assume is shown in Fig. 4.According to this modification, instead of the reciprocating carriage, ashaft 40 is rotated from motor 10, as by gears 41 and 42. Said shaftrotates feed screw 6 by means of a worm 43 and worm wheel 44. To permitready hand feeding, the worm wheel may be detachably connected to shaft6as by friction clutch 45, which is mounted on a sleeve on the end ofsub shaft 50 and resiliently pressed against a face of the worm wheel byspring 46 and pinned to shaft 6' by pin and slot connection 47, 48. Tofeed by hand, the operator first pushes in on the hand wheel 20 todisengage the clutch and then rotates the hand wheel in the desireddirection.

As before, I mount one of the contacts 27, 30' on the member 40 actuatedby the motor to cause relative transverse movements of the contacts.Inthis instant contact 30 is made circular and is, as before, providedwith a hi h spot 50 (see also Fig. 5). Current is siown as led intocontact 30 by brush 51 connected to motor 10. Other parts in this figureare numbered to correspond to the parts of Fig. '1. and their operationwill be'understood without repetition.

From the foregoing the operation of my invention will be clear. As longas the arc is of the proper length, magnet 22 is unable to overcome thepull of spring 28, and all feed parts are stationary. When the arclength becomes too great, contacts 27 and 30 are'closed, starting motor10, causing rubbing on the contact surfaces, and starting the automaticfeed which continues 7 until spring 28' overcomes the decreasing manetic pull. This break of the contact wil always be sharp and occur atthe high point on contact 30, thus leaving the hand feed free. It willof course be understood that there need not be a complete break betweenthe contacts 27 and 30 to efi'ectthe purpose of my invention, since ifgraphite or similar contacting surface is employed for at least one ofthe contacts, a stoppage of the motor may be secured by decreasing thepressure between the contacts to a small amount, so that the resistanceacross the gap will be sufiicient to prevent enough current flowing tooperate the motor.

In accordance with the provisions of the patent statutes, I have hereindescribed the principle of operation of my invention, together with theapparatus, which I now consider to represent the best embodimentthereof, but I desire to have it understood that the apparatus shown isonly illustrative and that the invention can be carried out by othermeans. Also, while it is designed to use the various features andelements in the combination and relations described, some of these maybe altered and others omitted without interfering with the more generalresults outlined, and the invention extends to such use.

Having herein described my invention what I claim and desire to secureby Letters Patent is:

I. In a feeding mechanism for projector lamps, the combination with acontrol coil connected across the arc, of motive means for effecting thefeed, a pair of contacts governed by the coil and in circuit with saidmeans to render the same operative, one of said contacts having aninclined face and being connected to said means so as to be movedtransversely to the other contact for the purpose specified.

2. In a feeding mechanism for projector lamps, the combination with acontrol coil connected across the arc, of motive means for efiecting thefeed, a pair of contacts governed by the coil and in circuit with saidmeans to render the same operative, one of said contacts being movabletoward and away from the other, and the last-named contact having aninclined face and bein connected to said means so as to be movetransversely to the other contact, the contact face of the first-namedcontact being polished and the contact moved-by the movement of thelast-named contact.

3. In a feeding mechanism for projector lamps, the combination with acontrol coil connected across the arc, of motive means for effecting thefeed, a carriage reciprocated thereby, pawl and ratchet mechanism forfeeding both electrodes by the reciprocation of the carriage, a pair ofcontacts the relative position of which is governed by said coil, one ofthe contacts being mounted on said carriage to be reciprocated therebyand having an inclined contacting surface.

4. A feeding mechanism as claimed in claim 3 wherein the surface of thereciprooatory contact slopes toward the other contact in the directionof the pawl, whereby the contact breaks when the pawl is out ofengagement with its ratchet for the purpose specified.

5. In a feeding mechanism for are lamps, the combination with a controlcoil, of an armature governed thereby, a pair of contacts one of which,is controlled by said armature, and means for moving said conposespecified.

In testimony signature.

,whereof I have afiixed my THEODORE HALL.

